Water Supply Outlook for Alberta

July 2005

Mountain Water Supply Summary

Due to an extremely wet June in all of the five major water supply forecast basins, forecasts have been discontinued for this year.

Total natural runoff volumes for the year so far (March - June) range from above average to much above average in the North Saskatchewan, Red Deer, and most of the Bow and Oldman River basins. Despite the very wet June, natural runoff volumes in the Milk River basin are below to much below average for the year so far due to previous dry months. However, any further precipitation will readily translate into runoff since soil conditions are now wet.

In the North Saskatchewan (Table 1) and Red Deer (Table 2) River basins, preliminary data indicates that natural runoff volumes for the March through June period are among the ten highest in up to 91 years of record.

Preliminary data in the Bow River basin indicates that recorded March - June natural runoff volumes were among the ten highest in 91 years of record for the Elbow and Highwood Rivers, inflow to Lake Minnewanka, and for the Bow River at Calgary. Natural runoff volumes in the Kananaskis and Spray Rivers were above average for the March - June period at approximately 25th highest on record. Since June's heavy precipitation did not fully reach into the back ranges of the mountains of the Bow River basin, the recorded March through June total runoff volume for the Bow River at Banff was near average (Table 3).

The total inflow volume to the Oldman Dam (near Brocket) was above to much above average for the March-June period, ranking near the 25th highest in 91 years of record. In the southern half of the Oldman River basin, natural runoff volumes for the same period were below average in the Waterton and Belly Rivers, and below to much below average in the St. Mary River. The heaviest precipitation during June fell to the north of these three southern rivers, and several months previous to June were dry. Flows at Brocket, however, have been high enough to result in above average natural runoff volumes in the Oldman River at Lethbridge for the March-June period (Table 4).

Natural runoff volumes in the Milk River basin were below to much below average for the March-June period, similar to the St. Mary River basin in that the heaviest precipitation fell to the north and previous months were dry. Volumes in the Milk River basin are just over half of average, ranking around the 22nd lowest on record (Table 5). However, this still represents a dramatic improvement during June, since March-May natural runoff volumes were less than a quarter of average.

Recorded volume data is preliminary and is subject to change. Check our Forecaster's Comments throughout the month for updated information regarding runoff conditions.


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